04 Feb Matter And Purity Of Substances

Joel, a student from the primary science tuition class in Miracle Learning Centre asked, “Can you imagine when you pump air into a fully inflated basketball, how does the ball get harder as you pump more air in?”

The primary science tuition teacher at Miracle Learning Centre replied, “This is because the air within it is being compressed and without having a place to escape to, it can only push against the ball from inside and make the ball harder! It’s fascinating isn’t it?”

Next, we will take a look at the heating curve and cooling curve of water.
At melting point, the temperature is constant. There is no increase in temperature.
This is because heat energy is absorbed to overcome attractive forces of attraction.
At boiling point, the temperature is constant. From the graph below, this happens at B. At A, water is in the liquid state and at C, steam is in the gaseous state. At B, the temperature remains constant.

This is because heat energy is absorbed to overcome attractive forces of attraction.

During cooling, at melting point, the temperature is constant.
This is because heat energy is given out to form bonds.

Max, a science tuition student at Miracle Leaning Centre asked,” What is the difference in melting point and boiling point of pure and impure substances?”
Miss Lin, a science tuition teacher at Miracle Leaning Centre replied,” Pure substance melt at a fixed melting point and boil at a fixed boiling point.
Miss Lin, a science tuition teacher at Miracle Leaning Centre further replied,” Impure substances melt at a lower melting point than the melting point of the pure substance and over a range of temperature. For example, pure ice melt at 00C but ice with salt added to it melt over a range of -20C to -50C.
Impure substances boil at a higher boiling point than the boiling point of the pure substance and boil over a range of temperature. For example, pure water boil at 00C but salt water boil over a range of 1020C to 1050C.
Susan, another science tuition student from Miracle Learning Centre asked,”Is there another way to test for the purity of a substance other than testing its boiling point and melting point?”

Miss Lin, a science tuition teacher at Miracle Leaning Centre replied,” Another way of testing if a substance is pure is by using chromatography. A pure substance produces only one dot as it is a pure substance. An impure substance is made up of more than one substance. Hence, the chromatogram of the impure substance produces more than one dot.

Chromatography separates the substances based on the relative solubility of the substance in the solvent and on the paper. The more soluble the substance is the further it will travel up the chromatogram. The less soluble the substance is the shorter the distance travelled up the chromatogram.”

Now, after explaining the properties of the states of matter and the boiling point and melting point, we have come to the end of our primary science tuition lesson at Miracle Learning Centre. Miracle Learning provides fun activities and worksheets for all primary science tuition students. We hope you have learnt something new today and we’ll see you in our next science tuition lesson!

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